sedimentary
Chert / Flint
Silicon Dioxide (Microcrystalline Quartz, SiO2)
Hardness of 7 on the Mohs scale, colors vary from gray, brown, white to black, waxy to vitreous luster, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors vary from gray, brown, white to black, waxy to vitreous luster, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
Formation & geological history
Formed through the diagenesis of silica-rich deep-sea ooze, skeletal remains of marine organisms (like diatoms or radiolarians), or as nodular replacements in limestone and chalk during the Mesozoic and Paleozoic eras.
Uses & applications
Historically used for making stone tools, arrowheads, and fire-starting (flint and steel); currently used in abrasive products, landscaping, and sometimes decorative cabochons.
Geological facts
Because of its sharp conchoidal fracture, chert was one of the primary materials used by ancient humans for making sharp implements and weapons.
Field identification & locations
Can be identified by its distinctive conchoidal (shell-like) fracture, waxy luster, and high hardness that scratches glass easily. Commonly found embedded in limestone or as pebbles in riverbeds.
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